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** 	TITLE:		gb1987_polls		                                          ** 	
**	AUTHOR:	    Philippe Mongrain                                             **
**	DATE:		October 2022 					                              **	
**  VERSION:	Stata 16					                                  **	
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* Version control

version 16.0

* Import data

import excel surveys, firstrow sheet(gb1987) clear
destring _all, replace

* Generate survey date

gen date = date(polldate, "DMY")
format %tdMon_DD,_CCYY date
drop polldate
rename date polldate

* Generate election date

gen edate = 19870611

gen electiondate = date(string(edate,"%8.0f"),"YMD")

format %tdMon_DD,_CCYY electiondate

* Time of survey

gen time = (electiondate - polldate) - 1

* Generate mean vote intention value by day

bysort time : egen conservativevote = mean(conservative)
bysort time : egen labourvote = mean(labour)
bysort time : egen libdemvote = mean(libdem)

sort time

* Drop duplicates

duplicates tag polldate, gen(dup)
duplicates drop polldate, force
drop dup

* Reshape the dataset

rename conservative v_conservative
rename labour v_labour
rename libdem v_libdem

reshape long v_, i(polldate) j(party) string

rename v_ vote

keep polldate electiondate party vote poll time

order poll polldate electiondate time party vote

* Generate rank of parties

gsort polldate -vote

bysort polldate : gen rank = _n

gen first = party if rank == 1
gen second = party if rank == 2
gen third = party if rank == 3

bysort polldate : gen winner = first[1]
bysort polldate : gen runnerup = second[2]
bysort polldate : gen thirdplace = third[3]

* Generate poll margin

bysort polldate : gen pollmar = vote[1] - vote[2]

* Drop duplicates

duplicates tag polldate, gen(dup)
duplicates drop polldate, force
drop dup

* Misleading poll

gen misleading = 0 if winner == "labour" & pollmar >= 1
replace misleading = 1 if misleading!=0

* Save

drop if time == 0 | time == .

keep polldate pollmar misleading time

save "gb1987_polls.dta", replace